1. Field of the Invention
The present invention relates to a plastic optical fiber, and more particularly to a fluorinated plastic optical fiber that contains a rare earth component and a method for producing the plastic optical fiber.
2. Description of the Related Art
Generally, rare earth elements such as La, Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb can emit fluorescence by 4f-4f electronic transition in a 3+ ionic state. Optical fibers containing such rare earth elements can amplifying an input light signal due to a stimulated emission effect. Also, such optical fibers may function as an optical fiber laser that continuously generates the stimulated emission if the reflectivity of both ends of the optical fibers is properly tuned. At a wavelength in the range of 1.3 to 1.4 μm, which is a typical bandwidth for optical communication, Pr3+, Nd3+, Dy3+ and Tm3+ emit fluorescence. Tm3+ emits fluorescence at a wavelength in the range of 1.4 to 1.51 μm, and Er3+ emits fluorescence at a wavelength in the range of 1.5 to 1.6 μm.
However, such optical fiber amplifiers have generally not been put to practical use because Pr3+, Nd3+ and Dy3+ have a poor efficiency in emitting fluorescence in quartz glass at a wavelength in the range of 1.3 to 1.4 μm or 1.4 to 1.5 μm. Due to this, conventional optic fiber amplifiers have been manufactured by adding a rare earth element to a fluoride-based glass optical fiber, thereby improving the fluorescence emitting efficiency. For example, details regarding such procedures are disclosed in U.S. Pat. Nos. 5,071,460 and 5,567,219.
However, fluoride-based glass optical fibers have poor chemical durability and mechanical strength because their chemical bonds are easily broken down by moisture. In addition, they have a disadvantage in that the light transmittance and light amplification efficiencies of the fluoride-based glass optical fibers rapidly decreases with time. Particularly, such optical fibers are rapidly corroded at junctions between the optical fibers because those junctions are exposed directly to air and moisture when an outer protective coating is removed from the junctions.
It is also noted that conventional plastic optical fibers have been developed for use in Gigabit Ethernet that substitute for copper wire communication in local area communication networks. Generally, plastic optical fibers are chemically stable and exhibit superior usability at normal temperature ranges. However, the conventional plastic optical fibers have a disadvantage in that their application for an infrared region is restricted because a hydrocarbon (C—H) high polymer chain structure absorbs light having an infrared wavelength.
Accordingly, there is a need in the art for improved plastic optical fibers.